Experimental study of damage in granite

The results presented here on damage of a granite from the centre of France are obtained using new experimental devices and a specific methodology in which the relation between strain and stress is obtained at different; stag es of damage using local strain measurements under high pressure. Mechanica l tests have been undertaken under the load paths such as deviatoric compre ssion and isotropic compression. Thus, at different stages of damage, the e volutions of elastic and plastic characteristics are obtained. Variations o f Young's modulus, damage criterion and strength are presented as functions of irreversible volumetric strain considered as an internal damage variabl e. Induced anisotropy of mechanical properties clearly appears under isotro pic compression loading. For example, the ratio of lateral strain over axia l strain can reach 2.5 when the irreversible volumetric strain is equal to 1%.